INTRODUCTION Before discussing the doctrine of equivalents it is necessary to understand its origin and the reasons which lead to the application of the doctrine in the patent law cases. The Doctrine of Equivalents is a doctrine which was judicially originated by the U.S courts. There are various reasons behind establishment of the doctrine by the courts. Also the debate over the doctrine of equivalents has raging from more than 150 years, ever since the doctrine has come into existence. When we talk about the doctrine of equivalents as it is interpreted by the Supreme Court of the United States, several issues rise into prominence. It is prudent to note that the patent laws of all countries specify certain minimum conditions, which needs to be fulfilled, prior to the grant of the patent by the concerned authority. Talking about the position of the law in India, all such patent claims with regard to their infringement are governed by the Patents Act 1970. And therefore the concept which is important to be understood with the Doctrine of Equivalents is that of infringement. Simplifying it, whenever any violation of the patent holder’s rights takes place then it is to be known as infringement. Infringement takes place in two ways; one is the literal infringement where the infringer copies exactly the same product or process of the patent holder and hence it leads to a direct and clear infringement. Second is the non-literal infringement where the infringer makes certain minor changes and manipulations in the particular product or process of the patent holder. The Doctrine of Equivalents is a kind of non-literal infringement. In this paper the author puts forth to consider the feasibility of the goal of universal harmonization as regards to the interpretation of the doctrine of equivalents and the scope for adopting the same in the Indian Legal System. The author adopts a comparative approach and discussed the position of the applicability of the doctrine in different countries. NATURE AND SCOPE OF THE DOCTRINE OF EQUIVALENTS AND ITS LIMITATIONS Whenever there is a case of patent infringement in front of the courts there are two main stages which the courts follow in order to investigate the infringement claim. The first stage is to check whether the particular product or process is literally infringing the patented product or process and the second is to check the infringement under the doctrine of equivalents. The second stage mainly takes place when the first stage fails. By saying this it means that during the judicial determination if there is no literal infringements found then the courts apply the second stage which talks about infringement under the doctrine of equivalents. Equivalence means that a claim element and its counterpart in a product do substantially the same thing in substantially the same way to achieve substantially the same result. HISTORICAL BACKGROUND OF THE DOCTRINE The aforesaid doctrine was established by the judicial efforts to stop competitors from making insignificant changes and modification to the claimed invention, and adding nothing in order to avoid the literal infringement. The view point by the U.S Supreme Court where the court first applied the idea of equivalents over a century ago in Winnans v. Denmead aiming to secure the necessary protection to the inventors. This was a perceived beginning of the doctrine. In Winans the patent claim involved introduction of a new mode of operation for the railroad cars. The accused device employed the same mode of operation; however the geometrical form of the cars was different than that which was claimed by the patentee. The court held: “because the exclusive right to the thing patented is not secured, if the public are at liberty to make sufficient copies of it, varying its forms or propositions,…the patentee, having described his invention, and shown its principles, and claimed it in that form which most perfectly embodies it, is, in contemplation of law, deemed to claim every form which his invention may be copied, unless he manifests an intention to disclaim some of those forms.” Also in a Supreme Court case the expression “doctrine of equivalents” was used was McCormick v. Talcott. The issue concerning the doctrine arose out of a suit brought by the patentee against persons who had made an improvement in a machine known as the McCormick’s reaper of which the patented invention was also an improvement. The patentee charged infringement of the claim for the divider, or that part of the reaping machine, which separates the grain to be cut from that which is to be left standing. Justice Grier proposed dismissing the claim on the grounds that it is infringing improvement of the machine is lacking with the dividing-iron or its equivalent. “[The patentee] could not challenge other improvements of the same machine, different in form or combination, as infringements, because they perform the same functions as well or better by calling them ‘equivalents’”. Subsequent to these cases, the issue relating to the doctrine of equivalents came up in several cases, which led to the creation of several tests, which would help the Court find out whether an object is equivalent to the claimed invention. APPLICATION OF THE DOCTRINE OF EQUIVALENTS As it is a judicially created concept (by the U.S courts) the judiciary has laid down certain tests to apply the doctrine of equivalents. The tests are; i) Function-way result test, ii) Substantiality of difference test. The Doctrine was further established by the U.S courts in the case related to patent infringement of Graver Tank and manufacturing Co. v. Linder Air Products . In this case the Supreme Court adopted the “function-way result test” in order to find out the infringement in relation to the doctrine of equivalents. The test considered that whether the element in the infringing device performs substantially the same function in substantially the same way to achieve substantially the same result similar to that of the element in the patented claim. Nearly about 50 years after the Graver Tank’s case, the U.S Supreme Court acknowledged the doctrine of equivalents again in Warner –Jenkinson Co. v. Hilton Davis Chem Co. criticized and commented on the limited application of the function-way result test in Graver tank. The court said that this method of function-way result test is although a valid method but not the only method (particularly for mechanical products and devices) for the purpose of determining the equivalence. The court in this case threw the light on the other method that is “substantiality of differences test” as criteria to determine equivalence between the patented invention and the accused one. This test is a kind of objective test. The courts say that rather than relying on the unexplained subjective conclusions there should be objective evidence upon which the substantiality of the differences should rest. If a person skilled in art can discover the interchangeability of the accused and claimed product. The Interchangeability which is known is powerful evidence that a person skilled in art would have considered a change insubstantial. If the claimed and accused elements are recognized by those of skill in the art to be opposing ways of doing something, they are likely not insubstantially different. By this the Supreme Court is keeping in mind the scope of patent rights of a patentee to protect its patent and how to create a balance between both. LIMITATIONS TO THE DOCTRINE OF EQUIVALENTS The federal court’s decision in the landmark case of Festo Corp. v. Shoketsu Kinzoku Kabushiki Co. again threw a light on the law dealing with doctrine of equivalence. In this particular case there were two patents which were granted to Festo which were Stoll patent and Carroll patent, both were related to magnetically coupled rodless cylinders. While Festo was marketing its devices the SMC Pneumatics Inc and the defendant company started marketing a similar device. There were several issues which arose and which were discussed at stretch and then finally the case came up before the Federal Court, which gave a concept and came to a conclusion that prosecution history estoppel could arise at any time whenever any claim made by the plaintiff is narrowed at the time of prosecution in order to satisfy the requirements of the Statute. The Court also went on to discuss the interplay between the doctrine of equivalents and prosecution history estoppel by observing that when prosecution history estoppel is applicable, it will create a complete bar on the use of the doctrine of equivalents. This approach of the Festo Court is known as the Complete Bar Approach. However, the Festo controversy kept on going and did not end at the Federal Circuit Court. This is because an appeal was filed against the order by Festo. The Supreme Court unanimously rejected the Complete Bar Approach as propounded by the Federal Circuit Court. There were repeated clarifications made by the court that the principle does not restrain the inventors from assessing the from assessing the infringement against every equivalent to the narrowed element. Instead, the Supreme Court went on to establish a presumption by which the onus shifts to the patentee to show that the concerned amendment does not surrender the particular equivalent in question. The Court thereafter gave three ways by which the presumption could be rebutted. Therefore, we observe that the Court approached the issue in a flexible manner striving to maintain a balance between innovation and certainty. Apart from the Festo decision, there were number of cases like Ranbaxy Pharmaceuticals Inc v. Apotex Inc., Sheet Metal Workers Local Health and Welfare Plan et al v. Glaxosmithkline Plc it was held that the patent holders were not able to invoke the doctrine of equivalents when they had narrowed down their claim during the prosecution of patent.
 M.Scott Boone, “Defining and Refining the Doctrine of Equivalents: Notice and Prior Art, Language and Fraud,” 43 IDEA 645 (2003).  For further analysis of patentable subject matter, see Section 3 of the Indian Patents Act, 1970.  Nard Craig Allen, A theory of claim interpretation, Harvard Journal of Law and Technology, 14 (2000) 1-15. The doctrine of equivalents prevents subsequent inventors from stealing the patented invention by making insignificant changes that avoid infringing the literal language of the claims yet result in essentially the same invention.  56 U.S. 330 (1854)  Elizabeth Verkey, Law of Patents, pp.420-21 (Eastern Book Company, 2nd Edition)  56 U.S. 330 (1854)  However this does not rule out the usage of the expression prior to 1957 in lower courts. This is evidenced by the fact that in 1949, a reference was made to a doctrine, in a jury charge by Justice Nelson, riding circuit. This doctrine, distinguishing a defendant’s article of manufacture from a claimed invention, was referred to in the jury charge by Justice Nelson in Buck v. Hermance, 4 F.Cas.550 (C.C.N.D.N.Y. 1849, Case no. 2082). This case concerned a suit by the patentee Buck, against a manufacturer of stoves for an infringement of his patent, which claimed the combination of a fire-chamber with an extended oven and flues. Justice Nelson charged the jury to whether the patent was valid and whether there was any infringement. It is pertinent to point out the relevant parts of Justice Nelson’s charge here. It read as follows: “In order to be patentable, the charge must be substantial, as contradistinguished from formal. The new article must be different from the article on which it is claimed to be an improvement, not only in its mechanical contrivance and construction but also in its practical operation and effect in producing the useful result. This is not formal…” It is necessary to note that the emphasis on the Justice’s Nelson’s identity is not unwarranted as the same Judge, subsequently was the author of the Supreme Court’s decision in Hotchkiss v. Greenwood, 52 U.S. 248 (1850), wherein he required that a patentable invention evidence more skill and ingenuity than that required by an ordinary mechanic acquainted with the business.  61 U.S. 402 (1857)  Note Justice Grier’s opinion for the Court in this regard. He states, “the inventor of the first improvement cannot invoke the doctrine of equivalents to suppress all other improvements which are not colorable invasions of the first.”  The claim can be reproduced in the interest of clarity as follows: “I claim the combination of the bow L and the dividing-iron M for separating the wheat in the way described.”  Supra Note 6. One of the foremost criticism against Justice Grier’s opinion, noted by the author in Alan Klein, “The Doctrine of Equivalents: Where it is Now, What it is,” 83 J. Pat. & Trademark Off. Soc’y 515 (2001), relates to the failure of the honourable Justice to define the terms “doctrine of equivalents” or “equivalent”.  See the decisions in Union Paper-Bag Machine Co. v. Murphy, (1877) 97 US 120; City of Elizabeth v. American Nicholson Pavement Co., (1877) 97 US 126. Also note the scholarly opinion of Garde Tanuja, “Legal Certainty, Stare Decisis and the doctrine of equivalents”, European Intellectual Property Review, 27(10) (2005) 365.  339 US 605 (1950)  520 US 17, 41 USPQ 2d 1865 (1997)  Brilliant Instruments, Inc., v. GuideTech, LLC, No. 2012-1018, slip op., at page10-11  234 F.3d. 558 (2002). For further discussion on the case refer to John Richards et al., Symposium, Panel I: “The End of Equivalents? Examining the Fallout from Festo”, 13 Fordham Intell. Prop. Media & Ent. L. J. 727, 763 n.135 (2003); Michael J. Meurer & Craig Allen Nard, “Invention, Refinement and Patent Claim Scope: A New Perspective on the Doctrine of Equivalents”, 93 Geo. L.J. 1947 (2005)  This is the most common argument against the principle of doctrine of equivalents. This principle applies where a patent applicant narrow down the patent claim during the patent prosecution in order to avoid prior art or otherwise to address a specific concern that would have made the claim unpatentable. In essence, this principle bars the applicant from later on using the doctrine of equivalents to recapture what he had surrendered earlier. The noted cases relevant in this context are Shepard v. Carrigan, 116 U.S. 593 (Sup. Ct. 1885); Warner-Jenkinson Company, Inc. v. Hilton Davis Chemical Co., 520 U.S. 17 (Sup. Ct. 1997); Festo Corp v. Shoketsu Kinzoku Kogyo Kabushiki Co. Ltd. 535 U.S. 722 (Sup. Ct., 2002).  ibid  122 US 1831.  ibid  122 US 1831,at p. 1842. The presumption could be rebutted by demonstrating that the equivalent may have been unforeseeable at the time of the application; or that the reason behind the amendment bears only an indirect relation to the equivalent in question; or some other reason.  Subsequent to this case, the Federal Circuit in many cases was asked to consider the scope of narrowing the claims. See Andrew Tuck, “Honneywell International Inc. v. Hamilton Sundstrand Corp: A rose by an independent description does not smell as sweet”, Georgia Law Review, 39(4)(2005) 1521 at p. 1541.  350 F.3d. 1235 (2003).  2006 US Dist LEXIS 9687, Also See Dr. Unni’s work on the same; While discussing the use of the term ‘limitation’, the Federal Court’s opinion in a couple of cases warrants mention. The Court stated that, “It is preferable to use the term ‘limitation’ when referring to claim language and the term ‘element’ when referring to the accused device.” Festo Corp. v. Shoketsu Kinzoko Kogyo Kabushki Co., 234 F.3d 558 at p. 564 (Fed. Cir. 2000) (In note 1, wherein the Court referred to the decision in Dawn Equip. Co. v. Kentucky Farms Inc., 140 F.3d 1009 (Fed. Cir. 1998).
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